In accordance with an embodiment, described herein is a system and method for compacting a pseudo linear byte array, for use with supporting access to a database. A database driver (e.g., a Java Database Connectivity (JDBC) driver) provides access by software application clients to a database. When a result set (e.g., ResultSet) is returned for storage in a dynamic byte array (DBA), in response to a database query (e.g., a SELECT), the database driver determines if the DBA is underfilled and, if so, calculates the data size of the DBA, creates a static byte array (SBA) in a cache at the client, compacts the returned data into the SBA, and stores the data size as part of the metadata associated with the cache. In accordance with an embodiment, the DBA and the SBA can use a same interface for access by client applications.